This invention relates to a gas turbine engine with booster stage and, more particularly, to a gas turbine engine with booster stage wherein the booster stage may be utilized to provide improved performance for an inlet particle separator and/or anti-icing means for the gas turbine inlet.
Aircraft gas turbine engines are particularly susceptible to damage from foreign objects introduced into the air inlets of the engine. This problem has been most acute in the past with respect to relatively large foreign objects such as stones, birds, hail, ice and the like. With the advent of gas turine powered helicopters and other vertical takeoff and landing VTOL aircraft, smaller particles of foreign matter, such as sand and water, have become increasingly troublesome due primarily to the conditions under which such aircraft may be operated. Because of the VTOL capability, this type of aircraft may be utilized in areas where conventional airfields are nonexistent, such as in combat zones, and in other isolated areas. Helicopters and other VTOL aircraft are also especially suited for certain low altitude missions on both land and sea, including close combat support, search and rescue, and antisubmarine warfare. Under these and related conditions, substantial quantities of small foreign objects, such as sand and dust particles and droplets of water, may become entrained in the airstream supplied to the gas turbine engine. These particles, which individually have little effect on the engine, can cause very substantial damage when introduced into the engine in large quantities. For example, it has been found that the engine of a helicopter operating at low altitude in a desert environment can lose performance rapidly due to erosion of the engine blading by high velocity particles. In addition to erosion, extraneous matter, particularly salt water introduced into the engine in this manner, can cause rapid and destructive erosion.
It is therefore desirable to provide means for separating out the particles of sand, dust, ice, water and the like before the airstream is supplied to the engine. To be satisfactory, it is essential that the separator chosen to provide this function be effective in removing the unwanted particles from the airstream. High efficiency is particularly desirable in an aircraft separator in view of the large quantities of air and, consequently, the large quantities of extraneous particles consumed by a gas turbine engine.
Heretofore, particle separators have included collection chambers which either retained the extraneous matter until the engine was shut down, whereupon the particles were removed through a cleanout port by means of a vacuum hose or, alternatively, remove the particles during engine operation through a single outlet port by means of a blower located in the outlet port. Retaining particles of extraneous matter within the collection chamber of the separator during engine operation is disadvantageous due to the likelihood that particles striking the walls of the collection chamber will eventually be rebounded back into the passageway and hence into the engine inlet. Also, the collection chamber of the separator may fill and overflow into the passageway. Removal of the particles from the collection chamber through a single outlet during engine operation has heretofore required that a separate blower be provided in conjunction with the outlet port to draw out the particles of extraneous matter. Such a blower adds to the overall weight of the engine without increasing engine performance. In addition, conventional particle separators have not included means for preventing ice formations on the interior components thereof wherein the ice components may chip off and enter the engine inlet, damaging the rotating components.
Therefore, it is a primary object of this invention to provide a gas turbine engine with booster stage wherein the booster stage increases the power output and improves the performance of the engine as well as the performance of an inlet particle separator and/or eliminates the need for additional anti-icing means downstream from the booster.
It is also an object of this invention to provide a gas turbine engine with booster stage wherein the booster stage imparts a minimum temperature increase to the airflow therethrough so as to inhibit the formation of ice downstream thereof.
It is a further object of this invention to provide a gas turbine engine with booster stage, wherein the booster stage is driven at near constant speed by the power turbine of the engine and the airflow from the booster stage is matched to the airflow requirements of the engine by a plurality of variable inlet guide vanes in cooperation with variable bleed means in a manner which maintains the minimum temperature differential across the booster stage.
It is an even further object of this invention to provide a gas turbine engine with booster stage and particle separator wherein the airflow exiting from the collection chamber of the particle separator may be modulated so as to match the airflow from the booster with the airflow requirements of the engine.